Electric discharge lamp



y 9,- 1940- w. J. sc TT El AL 7,133

ELECTRIC DISCHARGE LAMP vFiled Nov. 3, 1938 INVENTORS" WiHiam Joseph ScoHt Harry Kebbell Bourne Patented July 9, 1940 UNITED STATES PATENT oFF cE ELECTRIC mscnanen LAMP WilliamJ. Scott and Harry K. Bourne, Rugby,

England, assignors to General Electric .Company, a corporation of New York Application November 3, 1938, Serial No. 238,659

In Great Britain November 3, 1937 2 Claims. "(01. 176 -126) This invention relates to electric discharge lamps and more particularly to lamps of the high vapor pressure type similar to those disclosed in the United States Patent 2,094,694 issued October 5, 1937. Such lamps are usually made with envelopes of quartz or high melting point glass, and we have observed that, the material in the neighborhood of the electrodes is frequently attacked and devitrified.

The object of this invention is to provide means for preventing this devitriflcation, and to that end it consists in providing means for protecting the wall of the envelope in the vicinity of the cathode from sputtering which may cause devitriflcation and from heat radiation from the cathode. This means may consist .of a shield between the cathode and the wall of the lamp such as a cylinder or sleeve of refractory material, for example, of tungsten, molybdenum or The material forming ti e. wall of the quartz. envelope will then be protected from sputtered material from the cathode, and the devitrification will be reduced owing to the temperature of the wall being reduced, and owing to the shielding from the discharge and the sputtered material.

. In the drawing accompanying and forming part of this specification three embodiments o the invention are shown inwhich Fig. 1 is a side elevational, partly sectional view of one embodiment of the invention,

. Fig. 2 is a similar view of another embodiment I of the invention, and

' Fig. 3- is a similar view of stint-another embodiment'of the invention. I

' Referring to the drawing the gaseous electric discharge device comprises a-tubular: envelopel of quartz, into which an electrode 2 is sealed.

Before sealing the electrode into the envelope it is flrstsealed into a cylinder 3 of quartz, which is then sealed into the envelope I in such maner that the walls of the cylinder are infclose proximity to but not in actual contact with, the walls of the envelope I. It willbe understood, of course, that the other end of the device is similar in structure to the end shown in the. drawing. The-electrodes are preferably thermionic, activated electrodes which serve alternately as anode and as cathode when the device is operated on alternating current; The sealed. envelope I. has a starting gas therein, such as argon, and a quantity oi-metal, such as mercury, the vapor of which .is luminosity producing during the operation-of the device. I

.In Fig. 2 a sleeve 4 of tungsten or molybdenum is inserted in the envelope 1, so that it surrounds the electrode-2. When'the sleeve is made of metal, as in this case, it may be utilized as a starting or auxiliary electrode by providing a current lead therefor. Y

. l i 'Inthe construction illustrated in Fig. 3 a thin sleeve of molybdenum or other suitable refrac-'- tory metal 4 is sealed between an inner quartz sleeve Sand the outer envelope I so that it forms II a barrier which will prevent devitriflcation from spreading from the inner quartz shield to the outer envelope. In this case the metal sleeve may be utilized as an electrode. t What we claim as new and desire to secure by M letters Patent of the United States, is:

1. An electric discharge lamp of the highpressure type comprising a tubular envelope of vitreous material, electrodes sealed therein at the ends thereof, a vaporizablematerial-therein, and I a sleeve of refractory metal fused into the end of said envelope and surrounding one of said electrodes, part of the vitreous material of said envelope beinginterposedbetween said electrode and saidmetal sleeve and covering'the major I portion of the-inner surface of said sleeve, said sleeve preventing devitriflcation of said envelope in the region of said electrode.

2. An electric discharge lamp of the-high pressure type comprising a tubular envelope of vitreous material, electrodes sealed therein at the ends thereof, a vaporizable material therein, and 

